Tony Johnson1, Richard van Noort, Christopher W Stokes. 1. Department of Adult Dental Care, School of Clinical Dentistry, University of Sheffield, Claremont Crescent, Sheffield S10 2TA, UK. a.johnson@sheffield.ac.uk
Abstract
OBJECTIVE: The effect of four different, commonly performed, metal-ceramic alloy, surface preparation stages, were investigated to observe surface compositional changes. METHODS: Two metal-ceramic alloys were examined (Pd/Ag alloy and a Ni/Cr alloy). Discs 12 mm diameter and 2mm thick were produced using the lost wax casting process. Prior to casting alloy ingots were examined using X-ray fluorescence spectrometry (XRF) to determine bulk composition. The four preparation stages were (1) devesting and Al2O3 blasted; (2) ground smooth and Al2O3 blasted; (3) oxidation firing; (4) firing cycle for opaque porcelain application. X-ray photoelectron spectroscopy (XPS) surface analysis was performed after each surface preparation stage to determine changes in surface composition. SEM with EDS was also used to identify surface composition. RESULTS: XRF and manufacturers compositional analysis of the alloys showed similar findings for the major elements. XPS analysis showed that at preparation stages 3 and 4 evidence of elemental migration to the surface (In with Pd/Ag alloy and Cr and Mn with Ni/Cr alloy). Alumina was also seen on the alloy surfaces, with SEM/EDS confirming Al2O3 particles embedded in the surface of the alloys. SIGNIFICANCE: Surface composition is very different from the batch composition. Surface preparation stage 3 is essential in bringing to the alloy surface elements which could be directly involved in the metal-ceramic bond. Elements and their oxides, in various forms, cover the surface of the alloys. Al2O3 particles can remain embedded in the alloy surface during porcelain application.
OBJECTIVE: The effect of four different, commonly performed, metal-ceramic alloy, surface preparation stages, were investigated to observe surface compositional changes. METHODS: Two metal-ceramic alloys were examined (Pd/Ag alloy and a Ni/Cr alloy). Discs 12 mm diameter and 2mm thick were produced using the lost wax casting process. Prior to casting alloy ingots were examined using X-ray fluorescence spectrometry (XRF) to determine bulk composition. The four preparation stages were (1) devesting and Al2O3 blasted; (2) ground smooth and Al2O3 blasted; (3) oxidation firing; (4) firing cycle for opaque porcelain application. X-ray photoelectron spectroscopy (XPS) surface analysis was performed after each surface preparation stage to determine changes in surface composition. SEM with EDS was also used to identify surface composition. RESULTS: XRF and manufacturers compositional analysis of the alloys showed similar findings for the major elements. XPS analysis showed that at preparation stages 3 and 4 evidence of elemental migration to the surface (In with Pd/Ag alloy and Cr and Mn with Ni/Cr alloy). Alumina was also seen on the alloy surfaces, with SEM/EDS confirming Al2O3 particles embedded in the surface of the alloys. SIGNIFICANCE: Surface composition is very different from the batch composition. Surface preparation stage 3 is essential in bringing to the alloy surface elements which could be directly involved in the metal-ceramic bond. Elements and their oxides, in various forms, cover the surface of the alloys. Al2O3 particles can remain embedded in the alloy surface during porcelain application.
Authors: Jing Qiu; Chun-bo Tang; Zhi-jun Zhu; Guo-xing Zhou; Jie Wang; Yi Yang; Guo-ping Wang Journal: J Mater Sci Mater Med Date: 2013-07-24 Impact factor: 3.896